anticoagulants service Flashcards
name example oral anticoagulant - direct acting oral anticoagulant
Dabigatran
Apixaban
Rivaroxaban
Edoxaban
name examples of vitamin K antagonist
Warfarin
Phenindione
Acenocoumarol
name some injectable anticoagulant - lmwh
Unfractionated heparin Enoxaparin - LMWH Tinzaparin - LMWH Dalteparin -LWMH Fondaparinux sodium
mechanism of action of warfarin
Vitamin K antagonist/vitamin K epoxide reductase inhibition
Acts on multiple coagulation factors
mechanism of action of DOAC
Dabigatran is a direct thrombin inhibitor.
Other DOACs act on Factor XA
Similar efficacy to warfarin
mechanism of action of LMWHs/fondaparinux?
LMWHs act on Xa and IIa
Fondaparinux on Xa ONLY
why are anticoagulants prescribed?
PROPHYLAXIS / PREVENTION of:
Deep vein thrombosis (DVT) Pulmonary embolism (PE) Mural thrombus (often in ventricle after MI or can be peripheral)
Treatment of acute ST-segment elevation myocardial infarction (STEMI) and Non-ST-segment-elevation myocardial infarction (NON-STEMI), unstable coronary artery disease (LMWH ONLY)
when is warfarin/ LMWH given
Atrial Fibrillation (AF) (all types)
after insertion of prosthetic heart valves
after surgery
clotting disorders (e.g. thrombophilia)
when are DOAC given?
after hip or knee replacement surgery
patients with non-valvular AF with one or more other risk factors such as previous stroke, diabetes mellitus
what are the advantage and disadvantage of LMWH (low molecular weight heparin)
A: rapid onset of action
predictable - dose-dependent plasma level
long half life
in convenience - pre filled syringes
D:
S/C administration: not liked by patients / compliance issues/difficulty with technique/ need for district nurse support/local side effects/disposal of syringes
Complex dosing regimes: depend on patient weight and indication, some expressed as units, some as mg-difficult to prescribe and dispense
Expensive: Clexane (enoxaparin) 40mg/0.4ml solution for injection pre-filled syringes 10=£30.27 1 year=£1105
what are the advantage and disadvantage of warfarin
A:
Cheap: 5mg 28=£0.70, 3mg=£0.67 1year ≈£20
Requires INR monitoring ( ≈£200 p/a)
INR monitoring demonstrates efficacy
> 60 years of use
Useful in most situations where oral anticoagulant needed
Specific reversal agent- vitamin K
Tailored to the reason for use and to patient (target INR)
Slow to clear – one missed dose and patient still anticoagulated
Dis:
INR control affected by diet, alcohol, weight loss/gain, illness, medication etc
Wide range of doses
Slow to stabilise INR
Difficult to stabilise in some patients
what are the advantage and disadvantage of DOACS
A: No monitoring required Tailored to the reason for use Few drug/food interactions Fast time to onset
D:
Expensive: Apixaban 5mg 56=£53.20 1 year = £638.40
Rapid clearance – one missed dose and effects lost
Less experience
Limited product licences
Specific reversal agent for dabigatran Praxbind®(idarucizumab, £2400 per dose) but not others
No test of efficacy
Dabigatran unstable in MDS trays and cannot be crushed (unlicenced use of other DOACs / warfarin)
what is Warfarin-International Normalized Ratio (INR)
An INR test measures how long it takes blood to clot
It is the ratio of the Prothrombin Time (PT) of the subject compared to a normal control
Normal clotting time is 10-14 seconds, with an INR of 1
Time in Therapeutic Range (TTR) = % of timeframe when INR in range (aim>65%)
INR targets
depending on how high the risk is to get thrombosis - you are given a different INR target -
higher risk = higher target
low risk = lower target - target = 2.5 and range is 2-3
the people effected:
Atrial Fibrillation (AF)
Venous thromboembolism (VTE)
Bioprosthetic heart valve in mitral position
Bio prosthetic heart valve with additional prothrombotic risk factors e.g. AF
higher risk for thrombus - if they have mechanical aortic valve
target of 3
range 2.5-3.5
highest risk of thrombus -
Recurrent VTE whilst on anticoagulants and control within target range
High risk mechanical prosthetic heart valves e.g. mitral valves
Mechanical prosthetic heart valves with additional prothrombotic risk factors e.g. AF
target of 3.5
range- 3-4
INR targets
depending on how high the risk is to get thrombosis - you are given a different INR target -
higher risk = higher target
low risk = lower target - target = 2.5 and range is 2-3
the people effected:
Atrial Fibrillation (AF)
Venous thromboembolism (VTE)
Bioprosthetic heart valve in mitral position
Bio prosthetic heart valve with additional prothrombotic risk factors e.g. AF
higher risk for thrombus - if they have mechanical aortic valve
target of 3
range 2.5-3.5
highest risk of thrombus -
Recurrent VTE whilst on anticoagulants and control within target range
High risk mechanical prosthetic heart valves e.g. mitral valves
Mechanical prosthetic heart valves with additional prothrombotic risk factors e.g. AF
target of 3.5
range- 3-4